Safety Warning
DIY auto repair can cause serious injury, fire, or vehicle damage. These guides are for informational purposes only. Always follow OEM torque specs, wear PPE, and consult a certified mechanic if you are unsure. You are solely responsible for your safety.
Tire Pressure Monitor Description And Operation
The Tire Pressure Monitor (TPM) system alerts the driver when a large change in the pressure of one tire exists while the vehicle is being driven. The TPM system uses the Electronic Brake Control Module (EBCM), Body Control Module (BCM), ABS wheel speed sensor inputs, Instrument Panel (IP) fuse block Reset button, class 2 serial data circuit, and the Instrument Panel Cluster (IPC) to perform the system functions. The EBCM contains the software to calculate relative tire pressure differences. The software requires approximately 30 minutes of straight line driving in each of the three speed ranges to complete the calibration process in order to have full capability for detecting a tire pressure condition.
The speed ranges are as follows:
- 24-64 km/h (15-40 mph)
- 64-113 km/h (40-70 mph)
- 113-145 km/h (70-90 mph)
Each speed range has 2 modes of tire pressure detection.
- Monitor Mode 1
- Monitor Mode 2
The EBCM learns the tire pressure calibration for each speed range independently. In Monitor Mode 1, the EBCM has only partially learned the tire pressure calibration for the speed range and has limited detection capability for a tire pressure conditions. In Monitor Mode 2, the EBCM has fully learned the tire pressure calibration for the speed range and has full detection capability for a tire pressure condition. Once the TPM system has learned the tire pressure calibration the EBCM monitors the ABS wheel speed sensor inputs, which will all be the same as the learned calibration if the tire pressures stay the same. If the pressure increases or decreases in a tire, so too will that tire's circumference and radius, which causes that wheel speed sensor input to change. The EBCM recognizes this change in wheel speed as a tire pressure condition. If the pressure in one tire becomes at least 69 kPa (10 psi) lower or higher than the other three the EBCM commands the IPC to turn on the LOW TIRE indicator via a class 2 serial data circuit. This indicator does not appear if the pressure is high or low in more than one tire, or if the system is not completely calibrated. The system does not alert the driver to which tire pressure is high or low. To turn off the LOW TIRE indicator refer to Tire Pressure Monitor Reset Procedure .
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When to See a Mechanic
Stop DIY work and contact a certified mechanic immediately if any of the following apply:
- • You smell fuel, burning insulation, or see smoke.
- • Brakes feel soft, pull hard to one side, or make grinding noises.
- • The engine overheats, stalls repeatedly, or misfires under load.
- • You are missing required tools, torque specs, or safe lifting equipment.
- • You are not confident in the next step or safety outcome.